Reactive air wetting and brazing of Al <sub>2</sub>O <sub>3</sub> ceramics using Ag–Nb <sub>2</sub>O <sub>5</sub>filler: Performance and interfacial behavior
Yudi Qiu, Shunjian Xu, Xiangzhao Zhang, Mingfen Zhang, Qinhan Guo, Beiji Wang, Guanjun Qiao, Guiwu Liu
Abstract
We firstly performed the reactive air wetting and brazing of Al<sub>2</sub>O<sub>3</sub> ceramics using Ag–(0.5‒12)Nb<sub>2</sub>O<sub>5</sub> fillers, where Nb<sub>2</sub>O<sub>5</sub> can react with liquid Ag and O<sub>2</sub> from air to generate AgNbO<sub>3</sub>. The contact angle of the Ag–Nb<sub>2</sub>O<sub>5</sub>/Al<sub>2</sub>O<sub>3</sub> system almost linearly decreases from ~71.6° to 32.5° with the Nb<sub>2</sub>O<sub>5</sub> content increasing, and the joint shear strength reaches the maximum of ~65.1 MPa while employing the Ag–4Nb<sub>2</sub>O<sub>5</sub> filler, which are mainly related to the formation and distribution of the AgNbO<sub>3</sub> phase at the interface. Moreover, the interfacial bonding and electronic properties of related interfaces were investigated by first-principles calculations. The calculated works of adhesion (<i>W</i><sub>a</sub>) of Ag(111)/Ag–O–AgNbO<sub>3</sub>(001) and AgNbO<sub>3</sub>(001)/Al<sub>2</sub>O<sub>3</sub>(100) interfaces are higher than that of the Ag(111)/Al<sub>2</sub>O<sub>3</sub>(110) interface, indicating good reliability of the Ag/AgNbO<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub> structure. The relatively large interfacial charge transfer indicates the formation of Ag–Ag, Al–O, and Ag–O bonds in the Ag/AgNbO<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub> structure, which can contribute to the interfacial bonding.